2018 Kansas Wheat Quality Tour report
The 2018 Wheat Quality Tour took place during April 30 – May 3, 2018. About 100 people actively scouted hundreds of Kansas wheat fields in 25 groups and along six routes (Figure 1). The groups left Manhattan and headed to Colby on day 1, from Colby to Wichita on day 2, and finally from Wichita to Manhattan on day 3.
Figure 1. Representation of the six routes (purple, green, pink, yellow, blue, and black) explored during the wheat quality tour. Image courtesy: Wheat Quality Council.
The Kansas wheat crop is currently facing many challenges, as described below. Consequently, the overall 2018 production estimate for Kansas resulting from the tour was 243 million bushels of wheat, compared to 282 million bushels estimated in 2017. Weather conditions during the months of May and early June will be crucial in determining where the final production will actually land.
Several wheat fields sampled in the western portion of the state (from Rush County west) were showing severe symptoms of drought stress, with exception of far northwest Kansas (Figure 2). These symptoms included current drought stress (curling of younger leaves, abortion of older leaves, and yellowing of the lower canopy), and long-term drought stress (extremely reduced plant height and biomass and delayed development). Many of the sampled fields were achieving later stages of development, such as flag leaf emergence and boot, and were only 9-15 inches tall due to the prolonged stress (Figure 2). The lack of growth will not only reduce the yield potential, but also create difficulty during harvest. For fields under these conditions, yield estimates of 25 bushels per acre or less were very common. A rain within the next few days is essential to improve crop conditions and ensure some level of harvestable grain yield. If no rain occurs in the next few days, producers will have to face the decision of whether to harvest a crop with extremely limited yield potential or to terminate the crop and switch to a summer crop.
Figure 2. Drought-stressed wheat fields in western Kansas. Symptoms include decreased crop biomass production and height (left, Gove County KS), and curled leaves, abortion of older leaves, and yellowing of lower canopy (right, Ness County, KS). Both fields were between Feekes 7 and 8 (second node to flag leaf emergence) and were about 9 to 13 inches tall. Photos by Romulo Lollato, K-State Research and Extension.
The 2018 Kansas wheat crop is anywhere from two to four weeks behind its normal stage of crop development. For instance, in previous years of the wheat tour, stages of crop development around the state ranged from early grain fill in south central Kansas to boot stage in northwest Kansas (Figure 3). This year, the furthest along fields sampled were in late boot or early heading stages in south central Kansas, and the majority of northwest Kansas is just now jointed (first node, Figure 3). This delayed development is a consequence of drought stress combined with below-average seasonal temperatures, as the departure from normal temperature during the growing season (October 1, 2017 to April 30, 2018) ranged anywhere from zero to minus 13.5 degrees F across the state (Figure 4).
The consequences of this delayed development will depend on the weather conditions during May and June. If conditions are cool and moist, as Kansas experienced in 2015, 2016, and 2017, the crop might still go through favorable grain fill conditions and produce a decent yield. However, if temperatures are normal or above-normal, and precipitation is below-normal, the crop will go through grain fill during warmer conditions (as development will occur later in the year as compared to past years, when there is a greater probability of warmer conditions), which can severely limit grain yield. For fields that are currently at boot stage (south central Kansas), ideal weather conditions would result in as many as 50 days or more until maturity. However, if conditions are warmer and drier-than-normal, the crop might only have about 35 days or less, consequently reducing grain fill duration. Likewise, where the crop is still at the jointing stages of development, ideal conditions would result in as many as 70 days until maturity. However, warmer conditions might reduce this period to 50 days or less, restricting wheat yield. Drought or heat stress during grain fill limits the photosynthetic production of sugars and decreases the accumulation of starch in the grain, reducing grain test weight and grain yield, consequently increasing the percent protein in the grain.
Figure 3. Comparison between estimated wheat growth stage as of April 30, 2018 (upper panel) and May 1, 2017 (lower panel). Note that the most advanced wheat fields in 2018 (boot in southeast Kansas) correspond to the less advanced wheat fields in 2017 (boot in northwest Kansas). Maps courtesy of Erick DeWolf, K-State Research and Extension.
Figure 4. Departure-from-normal mean temperature during the 2018 winter wheat growing season (October 1, 2017 through April 30, 2018). Map courtesy of Mary Knapp, Weather Data Library.
The majority of the state is showing symptoms of freeze damage in the leaves (Figure 5) but for the most part, the burn back to leaf tissue resulting from freeze should be mostly cosmetic and not result in yield reduction. However, some wheat fields sampled in the central region of Kansas, especially between McPherson and Edwards counties (and surrounding region) were showing signs of freeze damage to the stem and developing heads, including stem and head discoloration and mushy texture (Figure 5). The percent of tillers damaged by the freeze was field-specific and within the fields sampled by our group, ranged from zero to 38%, mostly in the five to 15% range. This freeze damage most likely results from the freeze events observed during April 8 and 16, when temperatures were held below freezing for several hours (for more detail on the freeze events, please check eUpdate issues 685 and 687. If the crop has enough moisture moving forward, it should help compensate for the lost tillers and yield reductions might be minimal. However, we advise producers to scout their fields for freeze damage before further investing in the crop, for example, with foliar fungicides. If the crop has been severely damaged by freeze, yield losses might be severe enough to justify no further investment in the crop.
Figure 5. Left: freeze damage to the stem (brown discoloration) and developing head (white discoloration), photo taken at Edwards County, KS. Upper right: cosmetic damage from freezing temperatures to the leaf tissue, apparent across the entire state. Lower center: white head discoloration due to freeze damage in McPherson County. Lower left: Field showing about 25% tiller abortion due to cold temperatures in Trego County, KS. Photos by Romulo Lollato, Extension Wheat Specialist with Kansas State University.
Stripe rust update
The incidence of stripe rust in the 2018 tour was very low and mostly in the second day of the tour when the group scouted south central Kansas and north central Oklahoma. While at low incidence at this time, stripe rust has been reported in Oklahoma for a few weeks and the recent rainfall events likely brought spores to Kansas fields. It will take approximately two weeks from the time spores are introduced to the fields until the lesions are visible to the naked eye; thus, we advise producers to scout their fields for the disease in the next few days. The majority of the state is still within the fungicide application window and in case the disease is present, producers still have the option to spray. This decision should take into account the yield potential of the crop, the crop price, disease incidence, weather conditions, variety susceptibility to the disease, and the costs of product and application.
The above factors are a few of the major challenges that the 2018 Kansas wheat crop is currently facing. While all should contribute to restricted wheat yields to a certain extent, the largest uncertainty when estimating wheat production at the state level is the weather during grain filling. Because the crop is severely drought stressed in western Kansas and two to four weeks behind in development for the majority of the state, cool and moist conditions during grain fill are essential to ensure a decent crop. If warm and dry conditions arise, the wheat yield potential can be severely limited.
Romulo Lollato, Extension Wheat and Forages Specialist
Erick DeWolf, Extension Wheat Pathologist
Mary Knapp, Weather Data Library